From the prior art, for example from the document WO 2008/151583 A2, systems for emergency lubrication are known, in which an electric pump is combined with a mechanical pump. During normal operation the electric pump serves to supply the lubricant. If the electric pump fails, perhaps due to a loss of power(the lubricant supply is maintained by the mechanical pump, which, during this, is driven by rotating components of the transmission. To prevent the mechanical pump from operating in parallel even during normal operation, however, a complex mechanism is required which switches on the mechanical pump for emergency operation, i.e. if the electric pump fails. Furthermore, the mechanical pump loses power if the transmission is stopped and the pump's rotation slows down. Thus, if a wind turbine is slowed down it is not reliably possible to avoid a shortage of lubricant.
The documents EP 2 351 950 B1 and DE 37 02 008 A1 disclose systems for emergency lubrication without a mechanical pump. Instead of the mechanical pump, these systems comprise a container in which lubricant is stored intermediately. The container is positioned at a high level, so the lubricant can flow down from the intermediate container into the transmission without further energy consumption. During normal operation the supply of lubricant to the transmission is designed as a dry sump lubrication system. On transition to emergency operation a valve opens so that the lubricant stored intermediately in the container can flow down into the transmission. Consequently the lubricant level in the transmission rises, so the dry sump lubrication changes to immersion lubrication.
However, there are transmissions in which immersion lubrication is insufficient. In particular, slide bearings can often not be satisfactorily supplied with lubricant by immersion lubrication.